This invention relates to an automated manufacturing system wherein in manufacturing many kinds of products, groups of processors respectively corresponding to treatments each extending over several steps and a conveyor (conveyor system) for carrying workpieces (pieces to be treated) to the respective groups of processors are arranged, and the treatment sequence, treatment conditions etc. of the multifarious kinds of workpieces are automatically obtained from input information, to control the conveyor, the groups of processors etc. This serves to operate them efficiently and organically so that the product management and the process management are optimized. More particularly, it relates to a processing system for semiconductor wafers for manufacturing semiconductor devices in the semiconductor industry.
Circuit elements for use in assembling semiconductor devices, integrated circuits, large-scale integrated circuits etc. are, in general, formed of semiconductor pellets. The pellets are obtained in such a way that circuit element regions arranged and formed in a thin semiconductor plate (wafer) in vertical and horizontal arrays are split at the boundaries thereof. In order to fabricate the circuit element regions in the wafer, a very large number of manufacturing steps are required. By way of example, a process for forming regions containing desired impurity atoms in a silicon wafer includes (1) the washing step of washing the wafer to render it clean, (2) the oxide film formation step of heat-treating the wafer to form an oxide film (SiO.sub.2) in the surface thereof, (3) the resist coating step of applying a resist (photoresist) onto the oxide film and then drying it, (4) the exposure step of causing a part of the resist to sense light, (5) the resist partial-removal (etching) step of partially removing the resist having sensed the light or not having sensed it, (6) the oxide film partial-removal (etching) step of removing the exposed oxide film by employing as a mask the resist partially remaining on the oxide film, (7) the resist removal (etching) step of removing the resist remaining on the oxide film, (8) the diffusion step of depositing the impurity atoms onto the exposed silicon or causing them to permeate the surface layer portion thereof by employing the oxide film as a mask and by situating the silicon wafer in an impurity atmosphere or utilizing such a technique as CVD (chemical vapor deposition), evaporation and ion implantation, and applying heat again to diffuse the impurity to a desired depth, and (9) the removal (etching) step of removing the unnecessary oxide film of the wafer surface, etc. The technique which begins with the resist coating step (3) and ends in the resist removal step (7) is usually called the photolithography, which is repeatedly used for the formation of the circuit element. That is, it is employed for the formation of an interconnection layer, the formation of a protective film for passivation, etc. besides the impurity diffusion.
In addition, the course of the steps in the wafer processing in which the wafer is subjected to the various treatments as above stated differs depending upon the kind of the products because the respective kinds of the products have different contents of treatments. In this regard, if the so-called flow-shop-type in which job equipment is arranged in the order of the steps is adopted as an efficient job form, the workpieces flow smoothly, but each kind of the product needs to have an equipment arrangement peculiar thereto. Accordingly, when it is intended to mass-produce the various products, stupendous installations are required, which eventually makes the mass production impossible in practical use. Granting that the equipment is disposed for the respective kinds of the products in order to permit such mass production, there is the risk that the arrangement of the equipment will soon become old-fashioned and useless because the development of the semiconductor engineering is remarkable and the changes of products are radical. This leads to the disadvantage that the equipment investment is wasteful, so reduction of cost cannot be achieved. Therefore, as the so-called job-shop-type in which groups of equipment for performing common jobs are collectively arranged, the adoption of an expedient as illustrated in FIG. 1 is considered. There are disposed a diffusion chamber 2 in which a plurality of diffusion devices 1 are arranged, an ion implantation chamber 4 in which a plurality of ion implantation devices 3 are arranged, a photoresist chamber 7 in which a plurality of photoetching devices 5 and exposure devices 6 are arranged, a CVD evaporation chamber 9 in which a plurality of evaporation devices 8 etc. are arranged, and a test chamber 11 in which a plurality of probers 10 are arranged. In the respective groups of installations, multifarious kinds of workpieces in large numbers are treated once. Since, however, many kinds (several hundred kinds) of workpieces having different manufacturing methods (several tens of methods) are caused to flow in large numbers (several tens of thousand) at the same time in the wafer processings, it is difficult to skillfully manage the flow. In addition, long periods of time are taken until the products are finished up. Another disadvantage is that many workers are required. The job space in which the wafers are treated needs to be always kept clean. Nevertheless, the large number of workers move round in the treatment chambers in such arrangement, so that dust adhering to clothes and dust adhering to a floor etc. scatter by flying up and that the wafers are stained to lower the available percentage. Especially, as the pattern of the circuit element becomes finer, the job space is required to be cleaner. In this regard, in case where products having a very fine pattern are to be fabricated, the expedient as above described cannot possibly manufacture the products at a high available percentage.
On the other hand, human beings are essentially difficult to sustain in their most efficient state for very long. In the aforecited manufacturing system, this is also a cause for prolonging the period of time for completing the products.
It is therefore considered that the particulars of the wafer treating steps are individually made automatic, thereby to make the job in each step efficient and to enhance the available percentage owing to the maintenance of a clean job space.
It is also considered to process the information of the management of the proceedings of the steps by the use of a computer.
In these systems, however, the automation of a single step is subjected to the computer control, and the product management cannot be said to be satisfactory when viewed from the manufacturing course of a single kind of product. Moreover, since merely the individual steps are made automatic and the respective steps are independent themselves, the wafers must be carried by the worker between the automatic machines or the treatment spaces. This results in inevitably causing the stains of the wafers between the respective steps. The existence of the worker in the moving path of the wafers is a fatal cause for staining them.